The patient was pyrexial with a temperature of 39°C and complaining of lower limbs pain predominantly at the right knee and at the right hip joint. He had suffered multiple events of otitis and tonsillitis.
A 5 year old boy presented with fever (39°C) and lower limbs pain predominantly at the right knee and hip joint. Two weeks before he had a sore throat, cough and rhinitis.
He had raised inflammatory markers: laboratory result demonstrated an increase of ESR and C-reactive protein and a neutrophilic leukocytosis. The patient had a limp and a physical examination revealed a narrow range of right hip movements.
He underwent an ultrasound (US) exam of the hips that revealed a moderate intra-articular fluid collection, without capsular and synovial thickening (Fig 1). These findings suggested a diagnosis of transient hip synovitis.
Two weeks after an anti-inflammatory therapy he showed pain relief. However, at US exam the intra-articular effusion persisted. Magnetic Resonance (MR) scan of the hip showed an area of bone marrow oedema in the acetabulum, with moderate edema of the surrounding soft tissues (Fig 2).
A plain film radiography of the hip was normal (Fig 3). These abnormalities suggested the diagnosis of osteomyelitis, supported by clinical signs and symptoms.
He was given parenteral antibiotics associated with anti-inflammatory therapy.
A month later, MR revealed a reduction of acetabular bone marrow involvement and soft tissue oedema (Fig 4); the therapy was therefore continued. At two months’ follow-up MR did not show any radiological abnormality (Figure 5) and patient was symptom free.
Acute haematogenous osteomyelitis (AHO) is a common paediatric problem. It is an inflammation of bone and bone marrow, usually caused by bacterial infections (most frequently S. aureus).
In children it typically occurs in long tubular bones. Involvement of pelvic bones is relatively rare (6.3-20%).
Early diagnosis prevents sepsis, chronic infection, growth arrest, and deforming bone damage. Unfortunately, diagnosis can be difficult.
Infections in neonates and infants are initially clinically silent. Young children may present with only limping or refusal to bear weight. In pelvic infection, irritation of the lumbosacral plexus can mimic lumbar disk disease, and extension into the iliac fossa can produce abdominal pain.
Screening laboratory studies often lack of specificity and sensitivity. ESR is the best laboratory test, but positive predictive value is <26%. Blood cultures can only be positive if there is bacteremia.
When AHO is suspected, plain-film radiography, as initial imaging test, can show soft-tissue swelling as early as 48 h after the onset of symptoms but shows bone destruction or periosteal reaction only after 7–10 days, whereas lytic changes are more delayed, requiring 50-75% bone destruction.
US represents an appealing, expeditious imaging modality for screening of paediatric patients with clinically suspected osteomyelitis. It may shows fluid collections contiguous to the bone, suggestive of osteomyelitis. US should then be followed by other imaging techniques.
Computed tomography (CT) may play a role in the diagnosis of osteomyelitis, showing increased bone-marrow density and, in certain instances, intramedullary gas and depicting soft tissue involvement. CT may also demonstrate areas of necrotic bone.
Skeletal scintigraphy has played a central role in expediting diagnosis. Its sensitivity and specificity exceed 90% when it is interpreted with knowledge of clinical findings. It seldom requires sedation and provides a whole-body survey, which is useful when symptoms are poorly localized and when AHO is multifocal, as occurs in about 6% of paediatric cases .The difficulty in separating bone-marrow processes from soft-tissue disease limits specificity and accuracy.
MR is a valid imaging modality, able to confirm and localize the infection or establish an alternative diagnosis. Reported sensitivity and specifity in the diagnosis of osteomyelitis range between 88-100% and 75-100%, respectively.
Compared to scintigraphy, MR can differentiate between bone and soft-tissue infections; however, whole-body examinations are not feasible.
Criteria for diagnosis of acute osteomyelitis are decreased marrow signal intensity on T1-weighted images and corresponding increased signal intensity on short-tau inversion-recovery (STIR) images or normal to increased signal intensity on T2-weighted spin-echo (SE) images because of oedema, hyperemia, and exudate. The combination of T1-weighted and T2-weighted images is essential to distinguish abscesses and fluid collections.
In conclusion, plain radiographs represent the initial imaging test. US is particularly indicated in paediatric patients. MR should be requested to confirm the diagnosis and define site and extension of the disease. If MR is not feasible or when symptoms are poorly localized, bone scintigraphy (ideally, leukocyte scans for acute osteomyelitis and technetium scans for chronic osteomyelitis) should be performed.
Osteomyelitis of the hip
1. Routine X-ray plain films (pelvis and bilateral hips) show slightly abnormal density and shape in the right hip joint and pelvic area. The general contour of the pelvic bones is largely intact, but the adjacent soft tissue shadow appears blurred, suggesting possible soft tissue swelling or effusion.
2. Ultrasound images show an anechoic or hypoechoic fluid dark area near the bone, indicating possible fluid accumulation or pus.
3. MRI sequences (including T1-weighted images, T2 or STIR-weighted images) reveal abnormal signals in the right iliac bone, iliacus region, and adjacent soft tissues, primarily as follows:
- Decreased signal on T1-weighted images;
- Notable high signal or enhancement on T2/STIR or after contrast administration;
- Some areas show fluid-like signals, suggesting abscess formation or significant exudate;
- Edema/inflammatory signals also appear around the hip joint and pelvic soft tissues.
These findings are consistent with acute inflammation, bone marrow edema, and soft tissue infection.
Based on the patient’s high fever (39°C), repeated throat and ear infections, local pain (mainly around the right knee and right hip), and imaging findings of abnormalities in the pelvis/iliac bone, these are characteristic of acute hematogenous osteomyelitis commonly seen in children. Bone marrow edema and adjacent soft tissue fluid/pus support this diagnosis.
In children, inflammation in the hip region necessitates considering acute septic arthritis. Although it primarily affects the joint cavity, imaging may also show synovial thickening and soft tissue swelling. If there were purely intra-articular effusion, it would more clearly indicate arthritis. However, in this case, the MRI findings of bone marrow signal changes lean more toward bone marrow infection.
Given the history of recurrent infections, local soft tissue abscess or metastatic focus from bacteremia should be ruled out. However, a pure soft tissue lesion typically does not cause significant bone marrow signal changes.
Chronic inflammation such as bone tuberculosis can also occur in children but usually follows a more progressive course with imaging features inconsistent with an acute bacterial infection. It typically presents with a slower onset of symptoms along with other clinical findings.
Considering the clinical presentation (acute high fever, lower limb pain), history of recurrent infections (otitis media, tonsillitis, etc., which often involve pathogens similar to those causing osteomyelitis), laboratory findings (if blood counts and inflammatory markers are significantly elevated), and imaging features (bone marrow edema, evidence of pus in soft tissues), the most likely diagnosis is acute hematogenous osteomyelitis (involving the right iliac bone and surrounding soft tissues). Should subsequent blood cultures or related bacteriological tests and CRP results be positive, they will further support this diagnosis.
Emphasize rest and immobilization, avoiding excessive weight-bearing and joint movement. Use braces or crutches if necessary to reduce load on the affected limb. Begin rehabilitation exercises only after pain and infection markers have substantially improved.
Frequency: 3-4 times per week;
Intensity: Light to moderate intensity, avoiding heavy weight-bearing;
Duration: 10-15 minutes per session, gradually extended based on pain tolerance;
Methods: Range-of-motion exercises (start with small passive movements, progressing to active functional training) and moderate isometric muscle strengthening (e.g., isometric contraction of the quadriceps and peri-hip muscles);
Progression: As inflammation and pain improve, introduce lower-limb muscle strengthening such as straight leg raises and elastic band resistance exercises.
Frequency: 3-5 times per week;
Intensity: Moderate intensity, monitoring pain and fatigue in the affected limb;
Duration: Gradually increase to 20-30 minutes per session, depending on recovery progress;
Methods: Once normal gait is largely restored, consider low-impact endurance training for the lower limbs (e.g., stationary cycling, low-impact water exercises), along with targeted coordination and balance training around the hip joint;
Progression: Pay close attention to bone strength and joint stability. High-impact or jumping exercises should be introduced only if there is no pain and recovery is complete.
Throughout the rehabilitation process, closely monitor local pain, swelling, and systemic symptoms. For children with fragile bones or weaker cardiopulmonary function, rehabilitation should be carried out progressively under the guidance of professional rehabilitation therapists and pediatricians to avoid relapse or worsening of joint dysfunction due to overly aggressive training.
Disclaimer:
This report provides a reference analysis based on the current imaging and clinical information, and it cannot replace in-person consultations or professional medical advice. If you have any questions or notice any changes in your condition, please seek medical attention promptly.
Osteomyelitis of the hip
